The present invention relates to lifts for watercraft, and specifically to lifts for both raising watercraft out of water for storage and lowering watercraft into water for use.
There are many benefits obtained from storing a watercraft out of water when it is not in use. In the water, a watercraft may be subjected to physical, abrasive damage from contact with pilings and docks, particularly if there is a storm or otherwise choppy weather. Slow leaks may develop that can both damage the operation of the boat or cause sinking through leakage into the boat or may damage the environment if contaminants such as fuel or lubricants leak from the boat. There is also the corrosive effect of algae in fresh water and, if salt or brackish water, then barnacles and other marine growth.
Accordingly, it is well recognized that owners of watercraft preferably take their watercraft out of water when not in use. There are many types of dry storage and dry dock configurations available. On an individual level, some owners use lifts that raise their watercraft above the water level and hold them there between use. Boat lifts may be in the form of slings or other systems that lift the boat out of the water.
Some common types of boat lifts have an actuation system that is mounted, at least primarily, under the water level. These actuation systems connect to a base that rests on the bottom of the body of water. A pivoting type of platform is attached to the base to raise and lower the watercraft on it. Conventionally, the platform is moved upwardly and downwardly by a hydraulic system that is mounted onto the base of the assembly and underwater. In some designs, the hydraulic piston uses extension force, i.e., the rod pushes up the platform as the rod is extended out of the cylinder during the raising of the platform. Accordingly, when in the raised, storage position, the rod is exposed out of the cylinder. Since the raised/storage position is the most common position (as the boat platform is only lowered during use), then the rod is typically exposed out of the hydraulic cylinder for a majority of the time. During this exposure, foreign matter, corrosion, dirt, marine growth or some other form of contamination can develop on the rod. The entire hydraulic assembly could possibly be damaged or at least have its efficiency reduced through the action of drawing the rod and any accumulated contamination back into the cylinder damaging seals, o-rings, and other cylinder parts that maintain system pressure. Importantly, in a system having hydraulic fluid that is not water soluble, there are oils or other contaminants that may leak into the water.
Another drawback in previous boat lifts where the hydraulic cylinder is mounted on the base of the lift is that there is a certain amount of water depth required when the actuated system is located substantially below the water. Therefore, for the previous boatlifts to achieve a greater lift range would require more water depth or significant design change.
A further drawback with actuation systems mounted on the bottom of a support frame is that the only access to the hydraulic system is underwater. For purposes of installation, inspection, maintenance or repair, it can be inconvenient to work underwater. Also there can be fouling or damage on or around the actuation system that is not visible and can only occur when the system is underwater. Actuation under these conditions could possibly cause accidental harm to the user, the boat, or the entire system because it is not visible to the user.
Accordingly, it is an object of the present invention to provide a lift for watercraft that overcomes the foregoing drawbacks. The lift of the present invention utilizes an actuator that pulls a cradle that is adapted to hold a watercraft out the water and holds it in a raised position out of the water. Additionally, the actuator itself is mounted such that it is above the base and substantially above the water level of the body of water in which the lift is located.
In one embodiment, a lift for watercraft has raised and lowered positions and is adapted to be mounted in a body of water. The lift comprises a substantially rectangular base having first and second pairs of vertical corner posts that are connected to and carry longitudinal parallel beams. The base further has two transverse beams connected to the longitudinal beams. The lift also includes a pivoting cradle attached to the base and watercraft support bunks connected to the pivoting cradle. The lift further includes a pair of actuators, each connected on one end to the pivoting cradle and on its other end to one of the first pair of corner posts. The actuators are operable for rotating the cradle upward and past its pivotable connection to the base to a raised lift position, wherein the raised lift position is over center. Further, each of the first pair of corner posts is adapted to be long enough that at least a portion of the corner posts is above a water level of the body of water in which the lift is mounted, and the actuators are connected to the corner posts in the portion of the corner posts above the water level. The lift may further include cradle retainers mounted on the first pair of corner posts, the retainers adapted to support the cradle in the raised lift position. The watercraft support bunks may be mounted on an angle onto the pivoting cradle. The actuators may be bidirectional hydraulic cylinders. Those hydraulic cylinders may have rods that move in an extension direction when the rods extend out of the cylinder and move in a retraction direction when the rods retract into the cylinder, and wherein the upward rotation of the cradle to the raised lift position is created by movement in the retraction direction of the rods into the cylinders. The rods may be substantially completely retracted into the cylinders when the lift is in the raised position. Each of the corner posts may comprise a telescoping leg whereby the lift height and level may be adjusted. The actuators may be above the water level when the lift is in the raised position.
In an alternative embodiment, the present invention includes a lift for raising a cradle on which a watercraft may be supported above a water level of a body of water for storage of a watercraft out of the water. The lift also may be used for selectively lowering the cradle into the body of water. The lift comprises a hydraulic cylinder having a rod for raising and lowering the cradle. The rod is moveable between a retracted position wherein the rod is substantially within the cylinder and an extended position wherein the rod is substantially outside the cylinder. The cradle is in a raised position when the rod is in the retracted position. The hydraulic cylinder is above the level of the body of water when the rod is in the retracted position.